A simulation method based on the dimension chain of a segment assembly is proposed to address the error accumulation problem in the assembly process of segment with socket joint. Furthermore, MATLAB simulation model is established and the Monte Carlo method is used to simulate and analyze the assembling process of segments. Results are as follows: (1) The angle of the joint surface at the longitudinal joint is the primary factor affecting the reliability of the ring assembly of the segment, which should be strictly controlled. (2) In a multiring assembly analysis, reliability of the assembly in the ring corresponding to the staggered assembly method is higher than that of the through joint assembly method under the same assembly tolerance control conditions. (3) The assembly tolerance of the segment with the socket joint applied in the Jiangxinzhou tunnel in Nanjing, China, is optimized, effectively enhancing the assembly reliability and quality.